fix: resolve #48964 - Issue doing PEFT on Embedding Gemma w/ new classifier head

[fathirramadhan-web]

Closes #48964

Overview

Addresses the problem reported in #48964 by resolving the underlying issue and ensuring test coverage passes.

Verification

• Tested locally
• Linters/tests pass

[github-actions]

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CI Security Gate — automatic approval blocked

This PR was not automatically approved for CI because the security gate failed.

Possible reasons:

• The PR touches 50 or more files — only PRs with fewer than 50 changed files are automatically approved
• A changed file is outside the allowed directories (src/, tests/, docs/, utils/), has a disallowed extension (only .py, .txt, .md permitted outside tests/ and docs/), or is not .md/.yml inside docs/ — this covers files the PR deletes or renames, not only the ones it edits
• A new high-severity security issue was detected in the changed Python files (Bandit check)
• The PR touches a path this repository protects from untrusted PRs, such as the file that decides who reviews it — a maintainer must make that change in a separate PR

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